This is far from an official word, but PSP Takeover is reporting that Sony is providing free replacement PSPs for those who have two or more dead pixels (well, free plus shipping). Sony's US customer support isn't open yet (8AM PST), but we'll try to give them a ring later in the day to see what's up.

Nintendo was replacing any DS with a dead pixel, not two or more, so hopefully Sony will meet that challenge.

PSP Dead Pixel problem fixed [TBlog]

Update: Gamespot has all the details. The short story is: wait a week or two, and if they still bother you, Sony will replace the screen.
Sony responds to PSP dead-pixel reportsGameSpot]

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